The essential B vitamin folate may be even more important to ensuring the future health of newborns than previously thought, suggests a new study published Monday in JAMA Pediatrics.

The researchers, funded by the National Institutes of Health, analyzed the medical records of over 1,500 mothers and their recently born children who had taken part in the Boston Birth Cohort study. The study first began in 1998, and it followed mother-child pairs for up to 9 years after a woman’s pregnancy. Researchers drew a sample of blood from the mothers just a few days after delivery in order to measure their folate levels. And the results of this revealed the higher levels were, the less likely their children were to grow up overweight or obese. The protective effect was especially significant in obese women — those who had healthy folate levels were 43 percent less likely to have obese or overweight children than obese women with the lowest levels.

"Maternal nutrition during pregnancy can have long-lasting effects on child health, as well as the health of a mother after pregnancy," said lead author Dr. Xiaobin Wang, of Johns Hopkins University in Baltimore, in a statement. "Our results suggest that adequate maternal folate may mitigate the effect of a mother's obesity on her child's health."

The Multi-Purpose Vitamin

For the longest time, doctors have known that pregnant women with a folate deficiency, especially during the first trimester, are at greater risk of delivering children born with birth defects of the brain, spine and spinal cord. Because of that risk, health organizations like the U.S. Public Health Service and the Centers for Disease Control and Prevention have recommended that all women from the ages of 15 to 45 take in 400 micrograms of folic acid, a synthetic version of folate, on a daily basis — whether through supplements or by eating various fortified grain products. Folate can naturally be found in many fruits and vegetables like raspberries, leafy greens, and lentils as well.

Among its many health benefits, folate improves insulin sensitivity, a protective factor against obesity, as well as promotes other metabolic changes related to obesity prevention. And some, but not all earlier research has shown support for a link between a mother’s level of folate and later childhood obesity. The current study, however, is the first to look at objective measurements of folate in mothers, taking into account mothers’ weight status at the time of pregnancy, the authors wrote. The latter bit is particularly relevant since maternal obesity is a risk factor for obesity in their children. Nearly 25 percent of expectant mothers don’t have enough folate in their system as it is, according to a 2015 study conducted by the Centers for Disease Control and Prevention.

"Folate is well-known for preventing brain and spinal cord defects in a developing fetus, but its effects on metabolic disorders, such as diabetes and obesity, is less understood," said fellow co-author Dr. Cuilin Zhang, a researcher at the Eunice Kennedy Shriver National Institute of Child Health and Human Development. "This study uncovers what may be an additional benefit of folate and identifies a possible strategy for reducing childhood obesity."

Zhang and his colleagues also found that obese mothers were less likely to have proper folate levels than their thinner counterparts. And the children born to obese mothers with lower folate levels generally had the least healthy metabolic profiles, indicating folate’s ever-present role in metabolism.

That said, the vitamin only went so far — after a certain amount, there was no added benefit to upping folate intake as far as reducing obesity risk. However, this threshold, 20 nanomoles per liter of blood, remained higher than the minimum baseline for folate deficiency, less than 4.4 nanomoles per liter, which likely would have been achieved by consuming 400 micrograms of folic acid a day regularly before pregnancy. Given that other research has found that obese women may need more folic acid to achieve the same levels of folate in their blood as thinner women, it may be time to readjust our current recommendations for how much folate pregnant women actually need, particularly for obese women.

“Our findings underscore the need to establish and ensure optimal rather than minimal maternal folate concentrations for preventing offspring adverse metabolic outcomes, especially among obese mothers,” the authors concluded.

Source: Wang G, Hu F, Mistry K, et al. Association Between Maternal Prepregnancy Body Mass Index and Plasma Folate Concentrations With Child Metabolic Health. JAMA Pediatrics. 2016.